1. Field of the Invention
The present invention relates generally to a punch change retainer for use in a punch and die assembly, and more particularly, to punch change retainer including a floating punch retainer which is adapted to reversibly provide different punch retaining locations about a longitudinal center line of the floating punch retainer.
2. Description of Related Art
During manufacture of sheet metal or similar products, it is often necessary to form one or more holes in the workpiece material forming the product. Typically, a punch and die assembly is used to form the holes in such applications, particularly where large production volumes of the products are required. A production punch and die assembly generally includes an upper die shoe supported for movement toward a lower die shoe. A punch retainer is typically mounted to the upper die shoe and secures a punch to the die shoe. The punch is movable towards a die bushing secured to the opposing die by means of a die bushing retainer. Typically, the retainers are removably secured, e.g., through cap screws, to their respective die shoes, and the punch bushing and die bushing are also removably secured in their respective retainers. The retainers are positioned on the respective die shoes to locate the punches and corresponding die bushings such that holes are provided at predetermined precise locations on the workpiece.
In order to maximize the use of the punch and die assembly, the punch and die assembly may be reconfigured in order to perform different production runs. Such reconfiguration may be accomplished by attaching the punch and die bushing retainers to the die shoes at particular locations associated with the product to be produced. Alternatively, some constructions of punch and die assemblies incorporate change retainer tooling in which a movable punch retainer body supports a punch and is located in a change retainer housing. The change retainer housing is typically formed as an elongated member having the movable punch retainer located at a nose end of the change retainer housing and an actuator located toward the other end of the change retainer housing. The actuator actuates a gagging member to move the movable punch retainer between an actuated position where the punch is extended to operate on a workpiece, and a retracted position in which the punch is moved in toward the die shoe to a position where it will not engage the workpiece during movement of the die shoe. By providing a plurality of punch change retainer tools on a die shoe and programming the associated actuators to activate the punches for predetermined hole stamping patterns on the workpiece located in the assembly, the punch and die assembly may be readily reconfigured to provide different stamping patterns through activation and de-activation of the select ones of the punches. Such change retainers improve the efficiency of setting up the tooling for a hole stamping operation by avoiding the necessity of removing punches which are not required for a particular operation, while enabling activation of punches to an engagement position without requiring manual installation of punches.
In order to ensure standardization of tooling associated with change retainers incorporating ball lock punch retainers, change retainer structures have generally been constructed in accordance with the North American Automotive Metric Standard (NAAMS) which positions the center of the punch tool a predetermined distance from a reference dowel positioned in a surface of the change retainer body that is in cooperating engagement with a surface of the die shoe. The dimensions specified by NAAMS provide a point of reference for designing tooling for punch and die assemblies incorporating change retainers.
Applications incorporating change retainers frequently position plural change retainers in nose-to-nose relation with each other in order to closely position the holes formed by the punches of the adjacent retainers. Generally, the spacing between punches located in adjacent change retainers has been controlled by the thickness of the material required at the nose portion of the retainer, as well as by dimensional constraints imposed by the NAAMS. Further, the cost of change retainers is relatively high compared to conventional stationary punch retainers such that variations in design from the standardized dimensional criteria for change retainers have generally not been economical.
There is a need for a change retainer capable of conforming to industry standards for locating the punch tooling while also readily providing for positioning of punch tooling in alternative positions, such as providing alternative spacing of adjacent tooling relative to each other, to meet a wider variety of job requirements in a punch and die assembly.